Effect of deformation rate on interfacial heat transfer coefficient in the superalloy GH4169 hot forging process

To evaluate the effect of billet deformation rate on the interfacial heat transfer coefficient (IHTC) during hot forging process, the upsetting test of wrought superalloy GH4169 on the hot flat die was conducted. The inside temperature field data of the billet and lower die under the deformation rate of 0 s−1, 0.04 s−1, 0.08 s−1, 0.1 s−1, 0.2 s−1, 0.4 s−1 were respectively collected through using a multi - channel data acquisition system. Besides, Beck's nonlinear inverse estimation method was adopted to calculate IHTC and analyze the effect of GH4169 deformation rate on IHTC. According to the research results, the deformation rate had a distinctive influence on IHTC. When the deformation rate φ̇z⩽0.08s-1, the IHTC is small due to the blocking effect of the oxide scale on heat transfer; but when φ̇z>0.1s-1, the oxide scale was exfoliated in layers under the action of shearing force and a great deal of deformation heat and friction heat have been generated in short time, which has made the heat transfer condition improve greatly. Finally, the peak value of IHTC correlates approximately with deformation rate by a Boltzmann function, and tends to be saturated when the deformation rate φ̇z>0.2s-1.